1. Field of the Invention
The present invention generally relates to measurement systems for use with press machines, and, more particularly, to method and apparatus for dynamically monitoring the operation of a press machine during workpiece production cycles to identify and evaluate the press and tooling dynamic deflection activity.
2. Description of the Related Art
A press machine applies a force to a workpiece so that the material acquires a desired formation as the die configuration is maneuvered into contact with the material in response to the applied force. Various press types perform manufacturing processes such as forming, punching, mold closing, compressing, bending, drawing or injection molding. Systems for monitoring the press operation serve a critical role in production applications by measuring certain performance parameters that indicate the stability and optimization of the operation. Conventional arrangements employ a series of sensors affixed to the press machine at certain locations to measure the load being developed within the major components of the press machine. The load measurements are evaluated against certain threshold levels to determine whether current load conditions exceed the tonnage capacity. Another approach recognizes that loads developed in the press machine could lead to alterations in the structural integrity of press components such as the upright support members. An array of stress-strain gauges affixed to selected areas of the press machine provide measurements indicating the load levels existing in these areas.
One aspect of press operation warranting special attention involves accurately measuring and identifying the vibration activity developed within the press structure. U.S. Pat. No. 5,094,107 describes a variety of dynamic influences contributing to the generation and severity of press vibrations. Of particular note is the fact that vibrational activity can influence the production activity at neighboring die stations because of its ability to be transmitted through the press structure, in a manner not unlike the characteristic propagation of a shock wave from its epicenter. It is therefore critical to provide a monitoring system capable of accurately measuring the vibrational activity.
The normal load testing apparatus used in conjunction with these conventional monitoring systems has typically taken the form of static press loading and dynamic press loading. Neither configuration, however, serves as a demonstration of how the press machine and tooling will truly perform under actual loading conditions. These load calibration mechanisms, essentially function as models from which predictions are made of the actual performance data based on simulations constructed from the results of calibration. Static press loading involves subjecting the press assembly to one or two known hydraulic cylinder loads under static (i.e., non-motion) conditions to derive standard deflection values only applicable for making a general static comparison of one press versus another. Dynamic press loading via load cells distinguishes over static test apparatus because this method supplies measurement data on a dynamic basis; however, the loading mechanism still only represents a semisimulation of actual die loading conditions. Load cells are normally installed in the press machine to measure the responsivity of the press to certain known test loads, representing only a simulation of the load conditions that would actually occur in the event that production-type die configurations were used in an actual parts process. Operating the press machine with the load cell in place allows data to be continuously acquired from which a simulation model can be constructed and used to predict the dynamic performance under die load conditions. These conventional systems, however, evidence no ability to furnish measurement data on a continuous basis relating to the actual vibrational motion occurring within the press machine during an actual manufacturing processing when the die stations are in use.